We request support for a program in basic research directed at elucidating at a molecular level the nature and mode of functioning of the Beta-adrenergic receptors for catecholamines. Catecholamines such as norepinephrine and epinephrine are of vital importance in the hormonal control of the entire circulation. These compounds act via stimulation of the membrane-bound enzyme adenylate cyclase which is in turn mediated by binding to specific Beta-adrenergic receptors. Although the impetus to our studies has been the desire to shed light on the basic biochemical processes underlying adrenergic control of the circulation, it has become increasingly clear that the best models for study of the Beta-receptor cyclase system are simple, homogeneous cell populations. Accordingly, much of our work is conducted with such simple model systems. This proposal has three major intimately linked goals, all involving primary focus on the Beta-adrenergic receptor as an approach to gaining increased understanding of the normal and abnormal hormonal control of physiological processes. These goals are: 1) to obtain detailed molecular information about the biochemical nature of the Beta-adrenergic receptor including the complete amino acid sequence as deduced from cDNA clones as well as the sequence of the entire gene; 2) to understand the way in which the receptor functions to translate the binding of an agonist ligand on the outer surface of the cell into activation of the guanine nucleotide regulatory protein and the enzyme adenylate cyclase within the plasma membrane. This will be done by performing reconstitution studies in artificial membranes wherein purified receptor and purified effector components are reunited and their functional interactions studied. 3) To understand the way in which receptor function is regulated both in the plasma membrane, as for example by covalent modification, and at the nuclear level in terms of the rate of transcription of the cellular gene for the receptor. The major focus will be on the problem of desensitization of adenylate cyclase to Beta-adrenergic stimulation. Such desensitization is a common result of the therapeutic application of Beta-adrenergic and other types of agonists. These studies will provide the first comprehensive picture of the mode of functioning of an adenylate cyclase-coupled receptor in which detailed information about receptor structure provides the basis for understanding receptor function and receptor regulation.